The present invention generally relates to typical food service, food-holding/warming systems employing a hot water steam bath with food tray/dish inserts. This system replaces the water/steam approach with an induction heating system.
Typical food service, food-holding/warming systems use food tray/dish inserts heated from below by a hot water steam bath, termed a “steam table.” Steam tables have proven effective, but have several disadvantages. Given the thermal inertia of the water, the steam is relatively slow to heat the food, and the temperature can be difficult to predict and control. Replenishment of the water, and particularly availability of gas if the steam tables are gas-driven, can also be an issue given the locale (e.g., an airport, remote location, etc.). Other disadvantages of steam table systems are the requirement for a water supply and associated drainage. Additionally, the induction system is substantially more energy efficient than the hot water/steam approach.
Food holding/warming systems typically use a variety of stainless steel pans, trays, bowls, etc. Existing steel pans are typically made of Austenitic 300-series stainless steel (particularly 303 stainless) because of its corrosion resistance, a NSF requirement. These are, commonly known in the cooking industry, as well as from a physics/materials point of view, as being non-magnetic. Induction heating/cooking inherently assumes and relies upon the use of magnetic material in pots, pans, etc. For example, if stainless steel is used, then induction heating/cooking would presume the use of cookware thought of as “magnetic,” such as 400-series stainless steel.
For these reasons, food service pans, typically made of 300-series stainless steel (specifically, 303), have not been heated using induction heating methods. This appears to have led the induction-cooking product industry to assume that an inherent incompatibility exists between service pans and the use of induction heating.
Additionally, in food holding/warming applications, it is often desired to use equipment that is as quiet as possible, given the presence of customers in this environment. Virtually all induction cooking equipment employs fans for cooling of the electronics, given the heat generated by the inverters and induction coils. The elimination of the need for fans is another advantage of the present invention.
Accordingly, it would be advantageous to provide apparatus, systems and a method for holding and warming food which is quiet and which provides efficient, fast and predictable heating control.
Definition of Claim Terms
The following terms are used in the claims of the patent as filed and are intended to have their broadest meaning consistent with the requirements of law. Where alternative meanings are possible, the broadest meaning is intended. All words used in the claims are intended to be used in the normal, customary usage of grammar and the English language.
“Magnetic permeability” means the measure of the ability of a material to support the formation of a magnetic field within itself, i.e., the degree of magnetization that a material obtains in response to an applied magnetic field. Permeability is the inductance per unit length. In SI units, permeability is measured in henries per meter (H m−1), or newton per ampere squared (N A−2).
“Relative magnetic permeability” means the ratio of the magnetic permeability of a material to the permeability of a vacuum, which is 1.0.